<?php
/**
* 将BMP图象转换成GD对象
* @author zhufu
* 
* @param mixed $src 资源文件
* @param mixed $dest    目标文件
*/
class bmp{
    
    public function __construct(){
        
    }
    

    public function bmp2gd($src, $dest)
    {
        // 打开资源文件
        if(!($src_f = fopen($src, "rb")))
        {
            return false;
        }

        //打开目标文件
        if(!($dest_f = fopen($dest, "wb")))
        {
            return false;
        }

        /*** grab the header ***/
        $header = unpack("vtype/Vsize/v2reserved/Voffset", fread( $src_f, 14));

        /*** grab the rest of the image ***/
        $info = unpack("Vsize/Vwidth/Vheight/vplanes/vbits/Vcompression/Vimagesize/Vxres/Vyres/Vncolor/Vimportant",
        fread($src_f, 40));

        //将数组值提升为当前作用域的变量
        extract($info);
        extract($header);

        /*** check for BMP signature ***/
        if($type != 0x4D42)
        {
            return false;
        }

        /*** set the pallete ***/
        $palette_size = $offset - 54;
        $ncolor = $palette_size / 4;
        $gd_header = "";

        /*** true-color vs. palette ***/
        $gd_header .= ($palette_size == 0) ? "\xFF\xFE" : "\xFF\xFF";
        $gd_header .= pack("n2", $width, $height);
        $gd_header .= ($palette_size == 0) ? "\x01" : "\x00";
        if($palette_size) {
            $gd_header .= pack("n", $ncolor);
        }
        /*** we do not allow transparency ***/
        $gd_header .= "\xFF\xFF\xFF\xFF";

        /*** write the destination headers ***/
        fwrite($dest_f, $gd_header);

        /*** if we have a valid palette ***/
        if($palette_size)
        {
            /*** read the palette ***/
            $palette = fread($src_f, $palette_size);
            /*** begin the gd palette ***/
            $gd_palette = "";
            $j = 0;
            /*** loop of the palette ***/
            while($j < $palette_size)
            {
                $b = $palette{$j++};
                $g = $palette{$j++};
                $r = $palette{$j++};
                $a = $palette{$j++};
                /*** assemble the gd palette ***/
                $gd_palette .= "$r$g$b$a";
            }
            /*** finish the palette ***/
            $gd_palette .= str_repeat("\x00\x00\x00\x00", 256 - $ncolor);
            /*** write the gd palette ***/
            fwrite($dest_f, $gd_palette);
        }

        /*** scan line size and alignment ***/
        $scan_line_size = (($bits * $width) + 7) >> 3;
        $scan_line_align = ($scan_line_size & 0x03) ? 4 - ($scan_line_size & 0x03) : 0;

        /*** this is where the work is done ***/
        for($i = 0, $l = $height - 1; $i < $height; $i++, $l--)
        {
            /*** create scan lines starting from bottom ***/
            fseek($src_f, $offset + (($scan_line_size + $scan_line_align) * $l));
            $scan_line = fread($src_f, $scan_line_size);
            if($bits == 24)
            {
                $gd_scan_line = "";
                $j = 0;
                while($j < $scan_line_size)
                {
                    $b = $scan_line{$j++};
                    $g = $scan_line{$j++};
                    $r = $scan_line{$j++};
                    $gd_scan_line .= "\x00$r$g$b";
                }
            }
            elseif($bits == 8)
            {
                $gd_scan_line = $scan_line;
            }
            elseif($bits == 4)
            {
                $gd_scan_line = "";
                $j = 0;
                while($j < $scan_line_size)
                {
                    $byte = ord($scan_line{$j++});
                    $p1 = chr($byte >> 4);
                    $p2 = chr($byte & 0x0F);
                    $gd_scan_line .= "$p1$p2";
                }
                $gd_scan_line = substr($gd_scan_line, 0, $width);
            }
            elseif($bits == 1)
            {
                $gd_scan_line = "";
                $j = 0;
                while($j < $scan_line_size)
                {
                    $byte = ord($scan_line{$j++});
                    $p1 = chr((int) (($byte & 0x80) != 0));
                    $p2 = chr((int) (($byte & 0x40) != 0));
                    $p3 = chr((int) (($byte & 0x20) != 0));
                    $p4 = chr((int) (($byte & 0x10) != 0));
                    $p5 = chr((int) (($byte & 0x08) != 0));
                    $p6 = chr((int) (($byte & 0x04) != 0));
                    $p7 = chr((int) (($byte & 0x02) != 0));
                    $p8 = chr((int) (($byte & 0x01) != 0));
                    $gd_scan_line .= "$p1$p2$p3$p4$p5$p6$p7$p8";
                }
                /*** put the gd scan lines together ***/
                $gd_scan_line = substr($gd_scan_line, 0, $width);
            }
            /*** write the gd scan lines ***/
            fwrite($dest_f, $gd_scan_line);
        }
        /*** close the source file ***/
        fclose($src_f);
        /*** close the destination file ***/
        fclose($dest_f);

        return true;
    }

    /**
    * 创建一个BMP文件
    * @author zhufu
    * 
    * @param string $filename   文件名
    * @return resource
    */
    public function imagecreatefrombmp($filename)
    {
        /*** create a temp file ***/
        $tmp_name = tempnam("/tmp", "GD");
        /*** convert to gd ***/
        if($this->bmp2gd($filename, $tmp_name))
        {
            /*** create new image ***/
            $img = imagecreatefromgd($tmp_name);
            /*** remove temp file ***/
            unlink($tmp_name);
            /*** return the image ***/
            return $img;
        }
        return false;
    }
    
    
    
}
?>